Automatic choke for carburetor



June 22,1965 M. BALL 3,190,623

AUTOMATIC CHOKE FOR CARBURETOR Filed Aug. 1. 1961 2 Sheets-Sheet 1 IN VEN TOR Mil/Z yrro F/VIKSf BY Y.

June 22, 1965 'r. M. BALL 3,190,623

AUTOMATIC CHOKE FOR CARBURETOR Filed Aug. 1, 1961 2 Sheets-Sheet 2 INVENTOR. 734077745 MZ ZZ United States Patent 3,190,623 AUTOMATIC CHOKE FOR CARBURETOR Thomas M. Ball, Bloomfield Hills, Mich., assignor to (Ihrysler Corporation, Highland Park, Mich a corporation of Delaware Filed Aug. 1, 1961, Ser. No. 128,412 2 Claims. (Cl. 26139) This invention relates to fuel charging systems for internal combustion engines and in particular to an improved carburetor for an automobile engine which prevents engine stalling due to lean fuel-air mixture at idle following a cold start, without providing an overrich mixture at road load.

It is customary to provide a thermostically controlled choke valve to restrict the fuel-air induction conduit of a carburetor during cold starting conditions. Immediately after the cold engine is started, the extent of choking required for engine idling is appreciable, but decreases rapidly in the first few seconds of idling in consequence of engine heating and frictional heating of the bearing parts which rapidly reduce the frictional load on the engine.

In order to prevent the engine from stalling immediately after a cold start, the bi-metallic thermostat spring controlling the position of the choke valve is usuallly predetermined to allow opening of the choke valve approximatelyof arc from the closed position. Within a few seconds after the engine is started, the aforesaid heating effects, particularly in the bearing parts, enable the engine to idle with a choke opening of approximately of arc. However, the thermostatic choke control spring is not readily responsive to these heating effects and restricts the choke opening to the 20? of are for the first several minutes of idling. During this time, the fuel-air mixture will be excessively rich and poor fuel economy will result.

The initial opening of the choke valve to the idling position in opposition to the force of the thermostatic choke control spring is commonly accomplished by pressure actuated means operatively connected with the choke valve and responsive to the low pressure in the induction conduit downstream of the usual throttle valve. When the throttle valve is opened beyond the idling position for operation of the engine at road load conditions, the thermostatic spring normally required to prevent engine stalling within the first few seconds after a cold start exerts too strong a closing force on the choke valve for road load conditions, with consequent poor fuel economy.

An object of the present invention is therefore to provide a simple, economically manufactured and highly efficient choke control for the carburetor of an automobile engine which enables the use of a comparatively light-weight thermostatic spring that readily yields to enable the opening of the choke valve during operation of the cold engine under road load conditions, yet which affords optimum choking to enable rapid starting of the engine without stalling or die-out during cold conditions, and which cause progressive opening of the choke valve during the first few seconds of engine idling, until in approximately three or four seconds after the engine is started the choke valve will open through approximately 40 of arc. Thus during the first few seconds of engine idling, the choke will open progressively as the bearing load on the engine decreases, thereby to achieve optimum efiiciency of engine operation and fuel economy during the warm-up period under both idling and road load conditions.

Another object is to provide such a choke control comprising a pressure actuated mechanism engageable with the choke valve to open the latter progressively to approximately 40 of arc, the pressure actuated mecha- 'ice nism being connected by means of a restricted duct with the low pressure of the induction conduit downstream of the throttle valve associated with the usual carburetor. Thus the low pressure downstream of the throttle valve is effective to open the choke valve, but the transmission of the low pressure to the pressure actuated mechanism is delayed by the restricted duct.

Another and more specific object is to provide an improved arrangement in a pressure actuated choke control comprising a chamber secured to the side wall of the carburetor induction conduit and partitioned by a pressure actuated diaphragm into a high pressure part, in communication wtih the induction conduit via a port in the latters side wall at a location upstream of the choke valve, and a low pressure part in communication with the induction conduit downstream of the throttle valve via the restricted duct. A swinging arm pivotally mounted in the high pressure part and operatively connected with the diaphrgam extends through the port and engages the choke valve to open the latter upon transmission of the low pressure downstream of the throttle valve to said low pressure part.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming apart of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a schematic view substantially through the mid-section of a carburetor embodying the present invention.

FIGURE 2 is a view similar to FIGURE 1, illustrating a modification.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to FIGURE 1, a particular embodiment of the present invention is illustrated by way of example comprising a carburetor 10 which may be of conventional construction having an upper annular attachment rim 11 for an air cleaner and a central fuel-air induction conduit 12, whereby combustion supporting air enters at the top. A large venturi 13 is formed integrally with the side walls of the induction conduit 12 and a small venturi 14 discharging at the throat of the venturi 13 is suitably supported with the conduit 12. Fuel is admixed at the region of the venturis by means of a nozzle discharging in accordance with customary practice into the small venturi 14. The fuel-air mixture is discharged from the lower end of the conduit 12.

The discharge of the fuel-air mixture is controlled by a throttle valve 15 pivotally mounted on a transverse shaft 16 at a location downstream of the venturi 13. A thermostatically controlled choke valve 17 pivotallymounted on transverse shaft 18 is provided in accordance with conventional practice upstream of venturis 13 and 14 for the purpose of providing fuel enrichment during cold operation of the engine.

The shaft 18 extends through the side wall of the conduit 12 and is splined to a crank arm 19 pivotally connected at 20 to a vertically shiftable actuating arm 21 having its lower end pivotally connected at 22 to a crank arm 23 pivotal about the axis of a fixed spindle 24. A bi-metallic thermostat spring element 25 having one end secured to the spindle 24 extends spirally around the latter and terminates in a free end 26 engaging the lower end of arm 21 at the region of pivot 22. In the usual instance, the thermostat element 25 will be located so as .9 to be responsive to engine temperature. During cold conditions, the thermostat element 25 is under tension yieldingly urging shaft 21 upward and crank arm 19 clockwise so as to hold choke valve 17 in the closed position. As the engine temperature rises, the tension in thermostat spring or element 25 relaxes to enable opening of choke valve 17 to a progressively greater extent under any given condition of air flow in the induction conduit 12.

In order to supplement thermostat spring 25 in controlling the position of choke valve 17 during the initial stages of engine operation after a cold start, a pressure chamber is provided comprising a flanged cup 27 secured at its flange 28 to the carburetor exteriorly of the conduit 12 by means of screws 29. A flexible diaphragm 30 also secured between the flange 28 and juxtaposed portion of carburetor 10 by bolts 29 partitions the chamber into a low pressure chamber part 31 and a high pressure chamber part 32. A coil spring 33 disposed between the low pressure side of diaphragm 30 and the opposite base of cup 27 yieldingly maintains diaphragm 30 in a predetermined position as shown and resists its leftward movement.

Pressure actuation of diaphragm 30 is accomplished by means of a duct 34 having its upper end in communication with low pressure chamber part 31 and having a lower end in communication with induction conduit 12 at a location downstream of throttle valve 15. A bleed restriction 35 in duct 34 effects a delayed action of diaphragm 30 in response to a drop in pressure downstream of throttle valve 15. In order to enable immediate response of diaphragm 36 to a pressure rise downstream of throttle valve 15, a by-pass duct 36 including a valve seating chamber 37 is provided in parallelism with bleed restriction 35. A spherical check valve 38 normally closes by-pass duct 36 when the pressure downstream of throttle valve is lower than the pressure within chamber part 31, but is readily unseated to establish communication between chamber part 31 and conduit 12 when the pressure downstream of valve 15 exceeds the pressure within chamber part 31. Chamber part 32 is vented at 39 to conduit 12 upstream of choke valve 17.

A plunger 40 slidably supported by the body of carburetor 10 is suitably connected at 41 to a central portion of diaphragm 30 and terminates at its opposite end in a vertical cam surface 42. The latter engages the outer swinging end of a choke operating lever 43 suitably secured to an extension of shaft 18 adjacent the exterior wall surface of conduit 12, so that upon leftward movement of diaphragm 30 and shaft 40 from the position illustrated in FIGURE 1, valve 17 is progressively opened.

In accordance with the foregoing, thermostat spring normally holds choke valve 17 at a closed starting position with a force determined by the engine temperature to which thermostat 25 is responsive. Immediately after the engine is started, the low pressure downstream of throttle valve 15 during engine idling begins to bleed pressure through restriction 35 and duct 34 from chamber part 31, thereby to cause a progressive leftward movement of diaphragm and plunger 40. In consequence, choke valve 17 will be opened progressively against the tension of thermostat spring 25 regardless of the temperature condition. The time required to open choke valve 17 and the maximum extent of such opening will vary somewhat in accordancewith the operating conditions of the particular type of engine. However, with the usual automotive engine, a progressive opening of valve 17 from approximately a closed position through approximately 40 of arc in a three to four second time interval has been found to be very effective to prevent initial stalling of the engine during cold starting, yet to enable efficient operation of the engine with optimum fuel economy after the first three or four seconds of idling.

A modification of the present invention is illustrated in FIGURE 2 wherein the parts corresponding to the parts of FIGURE I bear the same reference numerals, but are differentiated by letter subscripts. Thus in FIG- URE 2 the carburetor 10 comprises an upper air horn portion 10a and a lower body portion 10b suitably secured together and spaced apart by a gasket comprising an extension of flexible diaphragm 30a. The latter extends externally of the induction conduit 12 and partitions a pressure chamber into two parts 31a and 32a formed by two castings 27b and 27a integral with the carburetor portions 101) and 10a respectively.

The carburetor is provided with the usual choke valve 17, throttle valve 15, and a thermostatic control 25 arranged and operated as described in FIGURE 1. A high pressure chamber part 32a is in communication with the interior of conduit 12 by means of a vent port 39a through which a swinging lever 43a projects. The latter is pivoted at 43b within the chamber part 32a and terminates in an inbent projection 43c engageable with the-choke valve 17 to open the latter upon counterclockwise pivoting of lever 43a. The latter is also provided with a downward extending loop 43d engaged within an eye opening 40b of a vertically shiftable shaft 40a having its lower end secured at 41a to the central portion of diaphragm 30a. The latter functions substantially in the manner of diaphragm 30 and is normally maintained in the position shown by coil spring 33a between its low pressure side and a portion of casting 27b.

Also as described in connection with FIGURE 1, duct 34 with its associated bleed restriction bypasses valve chamber 37 and spherical check valve 33 and is provided to connect chamber part 31a with induction conduit 12 at the location downstream of throttle valve 15.

In accordance with the construction illustrated in FIG- URE 2, as the pressure in chamber 31a is progressively bled through restriction 35 and duct 34 during the first few seconds of engine idling after a cold start, diaphragm 30a progressively moves down to cause lever a to engage swinging lever 4311 to swing the latter counterclockwise to progressively open choke valve 17 through approximately 40 of are from the closed position as before.

In either FIGURE 1 or 2, after the engine warm-up has progressed to the condition whereat thermostat spring 25 would normally hold choke valve 17 at the approximate 40 of arc opening, the auxiliary time delay pressure actuated mechanism will no longer be effective to control the position of the choke valve 17. The present invention eliminates the problem of engine stalling immediately after a cold start, regardless of the temperature condition acting at thermostat spring 25. Accordingly, greater freedom is possible in the selection of a thermostat spring 25 having the proper characteristics to assure efficient engine operation after the warm-up period. This is true because thermostat spring 25 need no longer be concerned primarily wtih the engine operating characteristics during cold starting and it is no longer necessary to make arbitrary compromises between efficient operation during engine starting and subsequent conditions of operation.

I claim:

1. In a fuel charging system for an internal combustion engine, an air inlet induction conduit, a choke valve in said conduit pivotal between open and closed positions and having an integral element pivotal coaxially therewith, a throttle valve in said conduit downstream of said choke valve, temperature responsive means for yieldingly urging said choke valve toward said closed position during operation of said engine in a cold condition, and operating means responsive to the position of said throttle valve to reduce stalling of said engine during the first few seconds after being started in said cold condition and for opening said choke valve. to a predetermined position to operate said engine immediately after said first few seconds, said operating means including a reciprocable plunger separable from said choke valve and adapted to move one direction into said engagement with said element to pivot said choke valve to said predetermined position, duct means for connecting said conduit at said location with said pressure actuated means to supply said operating pressure to the latter, and a time delay restriction in said duct means to retard transmission of said operating pressure to said pressure actuated means to delay opening of said choke valve for said first few seconds.

2. In a fuel charging system for an internal combustion engine, an air inlet induction conduit, a choke valve in said conduit comprising a valve shaft and blade, said shaft being pivotal about its longitudinal axis and extending transversely of said conduit, said blade being secured to said shaft to pivot therewith between open and closed positions, a throttle valve in said conduit downstream of said choke valve, temperature responsive means for yieldingly urging said choke valve toward said closed position during operation of said engine in a cold condition, and operating means responsive to the position of said throttle valve to reduce stalling of said engine during the first few seconds after being started in said cold condition and for opening said choke valve to a predetermined position to operate said engine immediately after said first few seconds, said operating means including a swinging arm separable from said blade and adapted to swing in one direction into engagement therewith to pivot said blade to said predetermined position and being separate from said blade to enable pivoting of the latter toward said open position independently of said arm, means yieldingly urging said arm oppositely from said one direction, pressure actuated means responsive to a predetermined operating pressure, equal to the low pressure in said conduit at a location downstream of said throttle valve when the latter is closed and said engine is idling, for swinging said arm in said one direction into said engagement with said blade to pivot the latter to said predetermined position, duct means for connecting said conduit at said location with said pressure actuated means to supply said operating pressure to the latter, and a time delay restriction in said duct means to retard transmission of said operating pressure actuated means to delay opening of said choke valve for said first few seconds.

References Cited by the Examiner UNiTED STATES PATENTS 2,705,484 4/55 Jorgensen et al. 236-92 2,803,442 8/57 Hausburg. 2,818,238 12/57 Olson. 2,9 18,266 12/59 Hamilton. 2,942,596 6/60 Carlson. 2,949,102 8/60 Duntov. 2,969,783 1/61 Braun. 3,013,544 12/61 Dermond et al.

HARRY B. THORNTON, Primary Examiner.

EUGENE F. BLANCHARD, Examiner. 

1. IN A FUEL CHARGING SYSTEM FOR AN INTERNAL COMBUSTION ENGINE, AN AIR INLET INDUCTION CONDUIT, A CHOKE VALVE IN SAID CONDUIT PIVOTAL BETWEEN OPEN AND CLOSED POSITIONS AND HAVING AN INTEGRAL ELEMENT PIVOTAL COAXIALLY THEREWITH, A THROTTLE VALVE IN SAID CONDUIT DOWNSTREAM OF SAID CHOKE VALVE, TEMPERATURE RESPONSIVE MEANS FOR YIELDINGLY URGING SAID CHOKE VALVE TOWARD SAID CLOSED POSITION DURING OPERATION OF SAID ENGINE IN A COLD CONDITION, AND OPERATING MEANS RESPONSIVE TO THE POSITION OF SAID THROTTLE VALVE TO REDUCE STALLING OF SAID ENGINE DURING THE FIRST FEW SECONDS AFTER BEING STARTED IN SAID COLD CONDITION AND FOR OPENING SAID CHOKE VALVE TO A PREDETERMINED POSITION TO OPERATE SAID ENGINE IMMEDIATELY AFTER SAID FIRST FEW SECONDS, SAID OPERATING MEANS INCLUDING A RECIPROCABLE PLUNGER SEPARABLE FROM SAID CHOKE VALVE AND ADAPTED TO MOVE IN ONE DIRECTION INTO ENGAGEMENT WITH SAID INTEGRAL ELEMENT TO PIVOT SAID CHOKE VALVE TO SAID PREDETERMINED POSITION AND BEING SEPARATE FROM SAID ELEMENT TO ENABLE PIVOTING OF SAID CHOKE VALVE TOWARD ITS OPEN POSITION INDEPENDENTLY OF SAID PLUNGER, MEANS YIELDINGLY URGING SAID PLUNGER OPPOSITELY FROM SAID ONE DIRECTION, PRESSURE ACTUATED MEANS RESPONSIVE TO A PREDETERMINED OPERATING PRESSURE, EQUAL TO THE LOW PRESSURE IN SAID CONDUIT AT A LOCATION DOWNSTREAM OF SAID THROTTLE VALVE WHEN THE LATTER IS CLOSED AND SAID ENGINE IS IDLING, FOR MOVING SAID PLUNGER IN SAID ONE DIRECTION INTO SAID ENGAGEMENT WITH SAID ELEMENT TO PIVOT SAID CHOKE VALVE TO SAID PREDETERMINED POSITION, DUCT MEANS FOR CONNECTING SAID CONDUIT AT SAID LOCATION WITH SAID PRESSURE ACTUATED MEANS TO SUPPLY SAID OPERATING PRESSURE OF THE LATTER, AND A TIME DELAY RESTRICTION IN SAID DUCT MEANS TO RETARD TRANSMISSION OF SAID OPERATING PRESSURE TO SAID PRESSURE ACTUATED MEANS TO DELAY OPENING OF SAID CHOKE VALVE FOR SAID FIRST FEW SECONDS. 